Phase transitions in Sr 0.61 Ba 0.39 Nb 2 O 6 :Ce 3+ : II. Linear birefringence studies of spontaneous and precursor polarization |
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| Authors: | P Lehnen W Kleemann Th Woike and R Pankrath |
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| Institution: | (1) Laboratorium für Angewandte Physik, Gerhard Mercator-Universit?t, 47048 Duisburg, Germany, DE;(2) Institut für Kristallographie, Zülpicher Stra?e 49b, Universit?t zu K?ln, 50674 K?ln, Germany, DE;(3) Fachbereich Physik, Universit?t Osnabrück, 49069 Osnabrück, Germany, DE |
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| Abstract: | The linear birefringence (LB) of Sr
0.61-x
Ba
0.39
Nb
2
O
6
:Ce
3+
x (SBN61:Ce) has been measured as a function of temperature within the range of . Large tails have been observed above the ferroelectric phase transition temperatures T
c
= 350, 328, 320 and 291 K for the concentrations x
= 0, 0.0066, 0.0113 and 0.0207, respectively. Within an Ornstein-Zernike analysis the critical exponents , and are determined. It suggests that pure SBN61 belongs to the 3D Ising universality class. Doping with Ce
3+
ions, which seem to act as random fields, enhances the relaxor properties. The critical exponents and of SBN61:Ce shift against those of the three-dimensional random-field Ising model.
Received 1 October 1999 |
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| Keywords: | PACS 64 60 Fr Equilibrium properties near critical points critical exponents - 77 80 Bh Phase transitions and Curie point - 77 84 Dy Niobates titanates tantalates PZT ceramics etc |
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